For example, in digital broadcasting, a program can be broadcast including captions in addition to images and sound. A TV receiver receiving programs of the digital broadcasting can, for example, display a caption included in a program such that the caption is superimposed on an image included in the program.
Incidentally, an information collecting device has been proposed which extracts caption information displayed in a specific region in a television image according to a predetermined extraction condition, and which stores the caption information (see Patent Document 1, for example).
In addition, there is a display device that extracts character data from image data output from a TV tuner, and which forcibly switches display data to the image data output from the TV tuner when the character data coincides with a keyword of a desired program (see Patent Document 2, for example).    Patent Document 1: Japanese Patent Laid-Open No. Hei 10-308921    Patent Document 2: Japanese Patent Laid-Open No. Hei 11-112874